In a paper bag, add 1/3 cup popcorn , fold over to close, and microwave for 90-120 seconds or until popped.
Repeat with the remaining bag.
In a very large bowl, combine the popcorn and cereal.
In a medium saucepan over medium heat, add the karo syrup and sugar.
Cook, stirring occasionally until the sugar has dissolved and the syrup is clear.
Add the peanut butter and stir until smooth and satiny, about 1 minute.
Pour over the cereal and fold with a wooden spoon to combine.
Add the chocolate chips and peanut butter cups and fold again.
Lay out on parchment paper to cool or enjoy warm.